This is an application to become one of the cooperating study centers in the Cryotherapy for Retinopathy of Prematurity Study. The CRYO-ROP Study consists of essentially two research components: (1) a clinical trial of the safety and efficacy of cryotherapy in reducing blindness in eyes with severe, high risk, ROP; and (2) a study of the natural history (in accord with the international classification of ROP) of retinopathy of prematurity in very low birth weight infants (less than 1251g). In this proposal we document the ability of our group of ophthalmologists and neonatologists to enroll, each year, 165 very low birth weight infants who have survived for at least 28 days in the natural history study. We anticipate that 12 of these infants will also develop retinopathy of prematurity severe enough to become eligible for enrollment to the clinical trial, and that an additional 4 patients will be referred to our center for enrollment to the trial. The CRYO-ROP Study is chaired by Earl A. Palmer, M.D., at the Oregon Health Sciences University. The Coordinating Center is directed by Robert J. Hardy, Ph.D., at the University of Texas Health Sciences Center, Houston.